The present invention is directed to a method and apparatus for producing vaporized hydrogen peroxide. More particularly, the invention is directed to a method and apparatus for producing sterilant grade hydrogen peroxide for use in form, fill and seal packaging machines.
Food products are often packaged in containers that have been sterilized to prolong shelf life of the contents. Such food products can include, for example, milk, juice, dried and/or particulate foods such as soups and the like.
When these products are packaged under aseptic packaging conditions, they can be stored for a substantial period of time at room temperatures without spoilage. The packaging processes require effective sterilization of the packaging material prior to filling the container formed from the packaging material. These containers includes, for example, well-known gable-top carton, as well as other like product storing containers.
In order to achieve the desired sterilization of the container to provide maximum practicable shelf life for the product, the containers are sterilized after bottom-forming and prior to filling with the product. The entire operation including container forming, bottom sealing, sterilization, filling and top sealing can be carried out in a form, fill and seal packaging machine, such as a Tetra Rex(copyright) packaging machine available from Tetra Pak(copyright), Inc. of Vernon Hills, Ill.
In a typical form, fill and seal packaging machine, a carton is erected from a tubular form and is placed on a mandrel. The bottom panels of the carton are folded and sealed to one another as the carton is indexed through the mandrel stations. Subsequent to bottom forming, the carton can have a fitment, such as the resealable plastic spout now available on containers, fitted and sealed thereto. Subsequent to fitment attachment, the carton is sterilized and is subsequently conveyed through the form, fill and seal packaging machine for filling and top fin sealing. The formed, filled and sealed containers are then discharged or off loaded from the machine for subsequent packaging and distribution.
Various devices and arrangements have been and are currently used to sterilize cartons on known form, fill and seal packaging machines. As disclosed in U.S. Pat. No. 6,094,887 to Swank, which patent is assigned to the Assignee of the present application and which patent is incorporated by reference herein, it is known to use ultraviolet energy, hydrogen peroxide, and a combination of UV energy and hydrogen peroxide to provide effective sterilization of containers. While various combinations of UV energy and hydrogen peroxide have been found to provide effective sterilization, the use of these two techniques adds considerably to not only the capital cost of the equipment, but the overall carton processing costs.
Known hydrogen peroxide application systems utilize electric heaters for heating and vaporizing hydrogen peroxide for subsequent application to the containers within the form, fill and seal machine. While these electric heaters work effectively, it has been found that the control systems for these heaters can be quite complex in that the temperature of the vapor-phase hydrogen peroxide must be measured so that an appropriate power can be supplied to the heaters. Such an arrangement requires temperature sensors as well as additional control equipment in order to maintain the vapor-phase hydrogen peroxide temperature within an acceptable range. It has also been found that electric heaters require a prolonged period for warming up after the equipment has been taken out of service. This can result in improper hydrogen peroxide vapor temperatures as well as the condensation of hydrogen peroxide on the electric heater elements.
It has also been found that electric heaters cannot always adequately control the output of vapor-phase temperature of the hydrogen peroxide. As such, hydrogen peroxide use may be greater than actually required thus increasing the overall process and costs.
Systems for vaporizing hydrogen peroxide are also known in which steam is intimately mixed with a liquid phase hydrogen peroxide solution which steam-hydrogen peroxide mixture is then applied to the containers. This technique has drawbacks in that it dilutes the hydrogen peroxide which can result in a less than optimal hydrogen peroxide solution concentration. In addition, such a system requires the storage of highly concentrated hydrogen peroxide which is undesirable. Accordingly, there exists a need for an apparatus and method for vaporizing hydrogen peroxide. Desirably, such an apparatus and method reduces or eliminates the possibility of diluting the vapor-phase hydrogen peroxide from a preset, desired concentration. Most desirably, such a method and apparatus permits rapid xe2x80x9cheat upxe2x80x9d and a controlled vapor-phase hydrogen peroxide temperature.
In accordance with the present invention, an apparatus for producing vaporized hydrogen peroxide, comprising a heat exchanger having an input for steam under pressure and an output for condensation and a conduit, extending within said heat exchanger, is provided. The conduit comprises an input for atomized hydrogen peroxide and air and a discharge end, such that when steam under pressure is added to the heat exchanger and atomized hydrogen peroxide and air traverse the conduit through the heat exchanger, the atomized hydrogen peroxide and air are heated and discharged through the conduit outlet as vapor.
In the preferred embodiment of the present invention, the conduit is a coiled tube which is placed inside a cylindrical tube. Atomized hydrogen peroxide and air flow through the coiled tube while steam under pressure is forced into the surrounding cylinder at a first end and is allowed to escape at a second end. The heat from the steam is thereby transferred from the steam to the coiled tube and the atomized hydrogen peroxide and air; vaporizing the hydrogen peroxide.
The coiled tube of the present invention is advantageously made of heat conductible metal which does not react to hydrogen peroxide, such as stainless steel or a composite metal having such properties as excellent heat conductability, malleability for easy shaping, inertness in the presence of hydrogen peroxide, and strength and durability. The device, of the preferred embodiment of the present invention, comprises a cylinder, having an input for steam and an outlet for condensation, with the conduit contained therein, the heat from stream being transferred to the conduit, to heat its contents, as the steam passes about the conduit.
The apparatus of the preferred embodiment of the present invention is advantageously connected to a packaging machine and the vapor is used to help sterilize packaging. The packaging is used for such products as milk and juice.
A more detailed explanation of the invention is provided in the following description and claims and is illustrated in the accompanying drawings.